There have been many different types of optical input devices for entering information into a computer by user manipulations of an input device, without the use of a keyboard. Such devices include absolute positioning devices such as light pens and digitized tablets, as well as relative positioning devices such as joysticks, track balls and mouse devices.
Such devices have typically been employed with cathode ray tube video monitors to enable a user to perceive visually the results of the manipulations relative to the information entered into the computer.
While such input devices have been satisfactory for single user applications, such devices did not enable a user to interact easily with a computer while making group audience presentations. More particularly, with the development of liquid crystal display technology, broader applications evolved. In this regard, by using a conventional overhead projector, computer generated information displayed on a liquid crystal display panel was able to be projected as an enlarged image onto a remote viewing surface or screen for group audience presentations.
With the advent of group presentations of computer generated images, it became highly desirable for a user or presenter of such information to interact with the computer without being confined at or near the computer controlling the projected image. In U.S. patent application Ser. No. 07/901,253 filed Jun. 19, 1992 entitled "COMPUTER INPUT SYSTEM AND METHOD OF USING SAME," there is described an optical input device, which enables a user to interact with a computer, while making a group audience presentation, without the need of being positioned at or near the computer. The optical input device enables the projected image to be modified or highlighted, as well as other control functions, such as double click, drag, and other mouse control functions. All of these control functions and others have been conveniently achieved by enabling the presenter to direct a high intensity light onto the surface of the projected image, whereby the manually directed beam of light is discriminated from the projected image and is interpreted to, in turn, provide control information directly to the computer generating the image to be projected.
While the above mentioned optical input device enables a user to interact easily with a computer during group audience presentations, the use of the large bulky overhead projector made it difficult, in some applications, for the user to transport the interactive system in a fast and convenient manner.
A compact projector including a built-in liquid crystal display panel, is disclosed in the U.S. patent application Ser. No. 08/059,550 now U.S. Pat. No. 5,321,450. The projector is compact in size, and easy to use. While such a compact projector is convenient to use, it would be highly desirable to have a built-in optical input device, which can be readily aligned with the projected image, for controlling it by enabling a presenter to direct a beam of light onto the projected image.